The invention is a process for coupling terminal acetylenes with propargylic alcohols to prepare eneynols.
The coupling of acetylenes is well-known. In the presence of alcohols, acetylenes and acetylenic alcohols are known to yield ethers, acetals, ketals and the like. In the case of alcohols of more than three carbons and simple aliphatic acetylenes, polymerization into nondistilled resins comlicates the often violent reaction. See e.g., Piganiol, Acetylene Homologs and Derivatives, Mapleton House, Brooklyn, NY (1950).
The dimerization of propargyl alcohol is known to give 2,4-hexadiyne-1,6-diol using cuprous chloride catalysts in the presence of oxygen. See also, Garwood et al., Chem. Ind. (1962) at p. 1684.
The coupling of 3,4-dimethylpent-1-yn-3-ol and phenylacetylene in the presence of tris(triphenylphosphine)rhodium (I) chloride catalyst is known to yield a mixture of products which includes homodimers and about 12 percent 2-phenyl-5,6-dimethyl-pent-1-ene-3-yn-5-ol and about 19 percent 1-phenyl-5,6-dimethyl-pent-1-ene-3-yn-5-ol. See e.g., Schmitt and Singer, J. Organometallic Chem. 153, 165-179 (1978) (Netherlands).
The preparation of certain eneynols otherwise generally proceeds by the reaction of Grignard reagents, see e.g., Crombie et al., J. Chem. Soc., 126 (1956), which are not suited commercially for larger scale production. Or, certain eneynols have been prepared by condensing formaldehyde with 1-buten-3-ynyl compounds, notably 1-buten-3-yne, also yielding significant amounts of tars. See. e.g., Gverdtsiteli, CA 42:6738 (1948).
What is needed is a process for preparing eneynols which is controllable and efficient both economically, especially in larger scale commercial applications, and materially, especially in reduction of unwanted tars and other polymerization by-products.